A two to five year prospective follow-up of 54 children and adolescents with obsessive compulsive disorder (OCD) revealed that, as a group, there was significant improvement from baseline. A subgroup of children had an episodic course punctuated by periods of abrupt symptom exacerbation and gradual remission. In addition, prospective systematic examination of children with Sydenham's Chorea (SC), (a variant of rheumatic fever), demonstrated that OC symptoms were present concomitantly with the onset of the movement disorder and were associated with the presence of antineuronal antibodies. Taken together, these suggested that a group of antineuronal antibody-mediated neuropsychiatric disorders might exist. One major thrust of our research is to determine the frequency and etiology of such disorders in order to establish effective intervention and prevention strategies. Other investigations include an ongoing activated PET (O15)study of OCD and its components, as well as drug-treatment studies of obsessive- compulsive "spectrum" disorders such as stuttering, and self-injurious and/or repetitive behaviors.